Glowing Blue DNA Gels

Stephen R. Lasky Stephen_Lasky at
Wed Apr 20 08:09:09 EST 1994

In article <2oshhf$2lo at>, forrest at
(Alistair Forrest) wrote:

> skralyf at (Frank Anthony Skraly) writes:
> >What the . . . ?
> >The last 2 times I ran agarose gels (TAE buffer, stained in dilute ethidium
> >bromide/water), I put them on the UV box and they glowed 
> >This made it very difficult to see the orange EtBr/DNA bands. 
> >The glowing would recede to bright blue spots on the gel after long destaining
> >periods in water, but would never go away.
> >Today I ran a well-behaved gel, but it had one blue dot.
> >Sometimes we use 1X EtBr solutions that have been sitting around for a day or 
> >two (in the dark), and I wonder if the EtBr turns into something else that 
> >fluoresces BLUE.  We've always done this, though, and we've never seen the BLUE
> >effect.
> Just sounds like you've got too much EtBr in your running buffer. To overcome
> this you could try including the EtBr in your gel (we use 20ul of 10mg/ml in
> a 40ml gel) or you could also try prestaining the gel in a concentrated solutionof EtBr before running. The advantage of this system is that as the EtBr is alsoelectrophoretically mobile and smaller than the DNA, it will run off the end of the gel. The EtBr is then diluted in the running buffer and as such it won't
> matter if the Et Br is recirculated to the front of the gel as by now it is
> so dilute it shouldn't pose any problem.
> Alistair Forrest

I've never seen EthBr glow BLUE.  In addition, why not just add the EthBr
to the gel after you melt it instead of letting it sit in staining solution
before running it?  

When I used to stain gels after electrophoresis, we would use EthBr in TAE
or TBE rather than water (therefore if you have to run your gel farther you
havent changed the salts) and we used to use the same EthBr solution for
quite a while.  As a matter of fact, that staining solution used to turn
blue, but that was from the BPB diffusing out of the gels.
Stephen R. Lasky, Ph.D.       Brown University/Roger Williams Medical
e-mail: Stephen_Lasky at         LandLine: 401-456-6572
A nuclear war could ruin your whole day.

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